In the last example on this page:
[[Alpha || Baker || Cray ], ]{2,3} and Delphi
The explanation begins with:
Two to three of Alpha, Baker, and Delta must be followed by and Delphi.
I believe the explanation should read:
Two to three of Alpha, Baker, and Cray must be followed by and Delphi.

Amber Matz

Aug 19, 2019

ePub

Page 57
Figure 2-18 source code

The source code is missing the closing </tr> tag

Note from the Author or Editor:I can’t tell if this is correct or not, since apparently he’s talking about the actual source markup in the ePub version.

This calculation is incorrect:
"Thus, if the browser window is 900 pixels wide, the side columns will each be 175 pixels wide, and the center column 550 pixels wide."
The flex basis for the nav and aside elements is 200px, and for the article element it is 600px (note that the text reads "The main element, on the other hand, has these styles" when it should say "The *article* element, on the other hand ...")
The negative space for a 900 pixel wide window will be 900px - (200px + 600 px + 200px) = -100px, i.e. 100 negative pixels. The shrink factor for the nav and aside are both 1, and for the article it's 2. Thus the shrink factor = -100px/(1*200px + 2*600px + 1*200px) = -1/16 = -6.25%.
So the shrinkage for the nav and aside is 1*(-1/16)*200px = -12.5 px each, and for the article it's 2*(-1/16)*600px = -75px, for a total shrinkage of 2*(-12.5px) + (-75px) = -100px, as expected.
Finally, the nav and the aside will each be 200px - 12.5 px = 187.5 pixels wide (not 175 pixels), and the article (i.e. the center column) will be 600px - 75px = 525 pixels (not 550 pixels).
I tested this out in dev tools, and this is indeed the result when the window is 900 pixels wide.